PolyVinyl Chloride. Actually polychloroethene, a thermoplastic polymer. PVC's durability, flexibility, and dielectric properties, along with its low cost, make it useful as an insulating material in copper cables. See also dielectric.
Permanent Virtual Circuit. A shared path established between two hosts through a packet network on a permanent basis. PVCs are preprogrammed in the routing tables of the transmission nodes throughout the network and are invoked based on various channel, channel group, or address information contained in the header of frames or packets. PVCs are defined on a permanent basis, until such time as they are permanently redefined, perhaps when the service provider rebalances the network to improve overall performance in consideration of changing usage patterns. Because the paths are predetermined and preprogrammed, network switches and routers can identify and exercise them quickly. PVCs are employed in frame relay and X.25 networks, as examples. A switched virtual circuit (SVC) is not preprogrammed, but is set up as the call is placed. See also channel, circuit, frame, frame relay, packet, path, SVC, virtual circuit, and X.25.